Very many not informed (6)
I believe the answer is:
untold
'very many' is the definition.
(I've seen this before)
'not informed' is the wordplay.
'not' becomes 'un' (prefix meaning 'not').
'informed' becomes 'told' (telling is a kind of informing).
'un'+'told'='UNTOLD'
(Other definitions for untold that I've seen before include "Lots" , "Story yet to be read" , "What's indescribable" , "Unspoken - inexpressible - uncounted" , "missing relations" .)